/Engine/Source/Runtime/Engine/Classes/Components/SkinnedMeshComponent.h
Transform a location/rotation from world space to bone relative space. This is handy if you know the location in world space for a bone attachment, as AttachComponent takes location/rotation in bone-relative space.
void TransformToBoneSpace ( [FName](API\Runtime\Core\UObject\FName) BoneName, FVector InPosition, FRotator InRotation, FVector & OutPosition, FRotator & OutRotation ) const